This invention relates to a grouping of fluid power valves to supply fluid power components such as cylinders, valves and the like. More particularly, the present invention relates to a fluid power interlock system including a circuit that will allow only one pneumatic output to be generated by the valve grouping at any one time. The present invention also relates to a fluid power interlock system having valves grouped together on a manifold, thereby eliminating the need for external tubing to perform the interlock function. The present invention further relates to a method of interlocking fluid power signals.
Fluid power valves, such as pneumatic valves, are often used to control devices such as linear or rotary actuators. Actuators may be employed to automate machinery and transport materials. In addition, actuators may be used to open and close other valves, such as process control valves, which control a process or manufacturing system. Very often a group of pneumatic actuator control valves are used to control a group of actuators. Due to the nature of the particular process or machinery, it may be desirable to ensure that only one actuator is in the actuated state at any given time. This can be achieved by preventing more than one valve from sending a pneumatic output at any particular time. In order to achieve such control, an interlock circuit is typically employed.
An interlock circuit for a pneumatic circuit may be either electrically or pneumatically controlled. Under either system, when one valve is actuated the other valves in the circuit are prevented from outputting a signal. An electrical interlock typically works by controlling the electrical signals to a valve grouping to prevent more than one solenoid of the valves from being energized at the same time. An electrical interlock can be achieved through electrical circuit components and/or by software if the valves are operated by a programmable logic controller. However, the use of an electrical interlock has a drawback in that the actual pneumatic output from the valve is not totally protected. For example, it is quite common that a solenoid operated pneumatic valve includes a manual override. An electrical interlock solution (circuitry or software) does not prevent manual valve operation; therefore, it remains possible to generate multiple pneumatic outputs and energize more than one actuator at the same time.
In a pneumatic interlock system, the pneumatic outputs from the valves are themselves controlled through pneumatic circuit devices to prevent more than one pneumatic signal from being generated at a given time. Therefore, even if a valve is manually actuated out of sequence, its output will not result in the untimely actuation of an actuator. A common well known pneumatic interlock circuit is shown in FIG. 1, and involves using a normally open valve 6 and a normally closed valve 7 for each actuator 50a-e. In addition, two xe2x80x9cORxe2x80x9d valves 8 are required for each valve pair to provide the pneumatic interlock control. This prior art pneumatic controlled interlock, however, is often considered impractical due to the number of components required to create the desired interlock function. In some applications, the additional cost and space requirements associated with the interlock function may be prohibitive. In addition, the pneumatic installation can become rather troublesome as a result of the many tubing connections required. For these reasons, a pneumatic interlock circuit is rarely implemented even though there are benefits that can be gained from its use.
Accordingly, it would be desirable to provide a pneumatic interlock system that is easy to assemble and uses a minimum number of components. It would also be desirable to provide a pneumatic interlock system having valve manifold, which interconnects the valves to provide an interlock function.
It is an advantage of the present invention to provide a fluid power interlock system.
It is a further advantage of the present invention to provide a fluid power interlock system having a pneumatic interlock circuit.
It is still a further advantage of the present invention to provide a fluid power interlock system including a valve manifold that provides the inter-valve connections to achieve a pneumatic interlock circuit.
It is yet a further advantage of the present invention to provide a fluid power interlock circuit including a first valve shiftable between a first and second state having an input connected to a pressure supply. The first valve further includes a first and second selectively operable outputs, and the second output is operatively connectable to a first actuator. The first output is operatively connected to the input of a second valve which is shiftable between a first and second state. The second valve has a third and fourth selectively operable outputs with the fourth output being operatively connectable to a second actuator. The third output is operatively connected to the first valve and provides a fluid power pilot signal thereto for permitting first valve 13a to shift from a first state to a second state. Based upon the arrangement of the first and second valves, shifting the state of either of the first and second valves interrupts the pilot signal thereby preventing the non-actuated valve from being actuated and shifting state. Accordingly, only one of the actuators can be energized at a given time.
In accordance with these and other advantages, the present invention provides a fluid power interlock system having a first and second double solenoid externally piloted valve. Each of the valves has a plurality of ports including a pressure port, a first and second pressure outlet port, and a first and second pilot port. The first and second valve each have a first state wherein pressure is supplied to the first outlet port, and a second state wherein pressure is supplied to the second outlet port. Wherein pressure at the first pilot ports assists the first and second valves to be shifted into the first state, and pressure at the second pilot ports assists the first and second valves to be shifted into the second state. The pressure port of the first valve is operatively connectable to a pressure source, and the first outlet port of the first valve is operatively connected to the pressure port of the second valve. The second outlet port of the first valve is operatively connected to a first actuator, and the first valve first pilot port is operatively connectable to the pressure source. The first outlet of the second valve is operatively connected to the second pilot port of the first and second valve, and the second valve second outlet port is operatively connectable to a second actuator. Whereby when either of the first and second valves is shifted to the second state to activate the corresponding actuator, pressure to the second pilot ports of each of the first and second valves is interrupted thereby preventing the other of the first and second valves from being shifted to the second state.
The present invention further provides fluid power actuator interlock manifold including a manifold body having first and second valve stations each including a plurality of ports to correspond with the ports of a sub-base mountable valve. The manifold body includes a channel connecting an air source port to first pilot ports of each of the first and second valve station ports. A second channel connects each of the second pilot ports of each of the first and second valve station ports, and the second channel is in communication with a first outlet port of the second valve station. A third channel connects the air source port to the pressure input port of the first valve station. A fourth channel connects a second outlet port of the first valve station to a first actuator port. A fifth channel connects a second outlet port of the second valve station to a second actuator port. A sixth channel connecting a first outlet port of the first valve station to a pressure input port of the second valve station.
The present invention also provides a method of interlocking fluid power signals comprising the steps of providing a first valve shiftable between a first and second state having a pressure input and a first and second selectively operable output, the first output being operatively connectable to a first actuator;
providing a second valve shiftable between a first and second state and having a pressure input and a first and second selectively operable output, the first output of the second valve being operatively connectable to a second actuator;
operatively connecting the second output of the first valve to the pressure input of the second valve;
operatively connecting the second output of the second valve to a first pilot signal port of the first and second valves for permitting the first valve to shift from the first state to the second state, wherein shifting from the first state to the second state of either of the first and second valves interrupts a flow of pressure from the second output of the second valve thereby preventing the non-shifted valve from being actuated and supplying pressure to a corresponding actuator.